Centrifugal pump



July 18, 193.9. w. F. HARLow CENTRIFUGALv PUMP Filed Jan.. 27, 195s Ins/enf r WdHcf Fred *Harlow A'H'ornej -A Patented July 1s, 1939 UNITED f -sTATEs PATENT OFFICE Application January 27, 1938, Serial No. 187,103 In Great Britain April 26, 1937 1 Claim.

1 This invention relates to centrifugal pumps and more particularly to the type used for pumping liquid` containing a quantity of abrasive solids,

for example grit, and liquors which vhave a dele- 5 terious eiect on the metals usually used for constructing such pumps, in which the metal parts of the pump which would otherwise come in contact with the liquids or liquors are protected by a layer of rubber. The rubber which is used for this purpose is of various compositions and the term rubber is used in this 'specification to include a resilient material having as an ingredient a proportion of metallic substance.

In such pumps it has been found necessary to l5 prevent the material being pumped from leaking into the glandwhere the pump spindle enters the pump.casing. The gland'is usually disposed on the side of the pump casing opposite to that containing the pump inlet and the amount of leakage to the gland has been lessened by providing auxiliary vanes on the back of the impeller, i. e. the face of the impellerv adjacent the side where the gland is located, which are designed to,have

a greater centrifugal action than the main pumping vanes on the front of the impeller.

It isn-found that in such pumps the life of the working parts depends largely on the thickness of rubber covering the various parts, but owing to considerations .of mechanical strength it has of which the various parts are sumciently substantial to resistsuchshocks' as may be caused by the entry of comparatively large solid masses into the pump. ',Ih'e thickness of rubber which it has been permissible to use has, therefore, been restricted to a comparatively :thin layer, which is usually about V4," tot/2 thick.

It is found that in pumps with auxiliary vanes as described above considerable wear takes place 40 ally project radially to the circumference of a Vby the high peripheral speed of the outer annular y part of the impellerwhen the pump is run may cause excessive wear: In consequence the rubber been found necessary to provide a metal structure at the tips of the vanes. I'he auxiliary vanes usu.

This wear is probably due to the fact that an- (cl. 10s- 115) Y may become perforated and detached from the metal it is designed to protect so that the exposed metal is liable to rapid destruction.

It is found thatthe excessive wear at the outer parts of the impeller, including the outer 5 parts of the auxiliary vanes, is prevented,rwhile preserving efficient operation ofthe pump, by the l invention according to which, in .spite of its not having beenI found possible to do without any metal core for the impeller and make the latter 10 wholly or mostly of rubber, the outer annular part of the impeller is made wholly of solid rubber. Y

Preferably, the invention is carried into eict by making the centre metal diseof the impeller 16 'of about the same diameter as the pumping vanes while the outer'annular part of the disc, together with the adjacent portions of the radially projecting auxiliary vanes, are made wholly of rubber united 'to the rubber covering of the remainder 20 ofthe impeller. y i

According to a further aspect of the invention the effect of the auxiliary vanes in maintaining the desired conditions at the gland is improved by so arranging the impeller that the height of the auxiliary vanes is progressively increased towards the impeller boss by atotal or final'amount equal to atleast twice the initial height at the periphery, which latter, in turn, is at least six times the dimension of the clearance between each vane and thecasing; the centre disc, in a cross-section of the impeller, may thus appear to have a reentrant hollow at the back of the impeller.

It is found that the ratio of the'height meassa ured in -the direction of the axis of rotation of the auxiliary vanes to the clearance between `the vanes and the back plate of the casing has an important effect on the action of thesevanes and it is desirable to make the vanes project from the centre disc as much as possible since the clear- 40 ance must be relatively large byreason of the rubber covering. It is undesirable, however, that the height of the auxiliary vanes .at the periphery of the disc should be large as this would increase the width of the casing at this point.

Even though the auxiliary vanes be comparatively shallow at their periphery they will still be better than vanes of. a uniform and shallow construction and it is found that even when the ,Y vanes are badly worn at their periphery the centre portions are suflicient to prevent'serious pressure at the gland.

The invention is illustrated by the accompanying drawing, which is a longitudinal section of a centrifugal pump embodying the invention.

'Ihe pumpcomprises an inlet I in the side 2 of the pump casing, and a discharge outlet 3 in the wall I0. 5 which passes through an opening in the rear wall 6 of the pump casing. An'annular space is left between the shaft 5 and the wall i, which is packed by suitable material I such as is` normally used in packing glands, so as to seal the pump chamber at the point where the shaft 5 enters. The shaft is carried in bearings (not shown).

The impeller comprisesa disc 4 and main impeller blades I I. 0n the side of the disc I, which is opposite the blades II and faces the wall 6,'

is mounted a set of auxiliary blades I2. The disc 4 and the auxiliary blades I2 are of larger diameter than the main blades II. 'I'he auxiliary blades and disc are so shaped that the height of the former measured parallel to the shaft 5 increases progressively towards the centre of the pump. v

The walls, 2, G and I0 and the main part o( the disc 4 are made of metal lined with rubber. The

The impeller is mounted on a shaft outer part 4a of the disc l is made of solid rubber, which is united with the rubber lining of the central part of the disc. 'Ihe tips I2a of the auxiliary blades I2 are also made of solid rubber, and are united to the rubber annulus la.

Having thus described the nature of the saidinvention and the best means I know of carrying the same into practical effect, I claim:

In Vcentrifugal pumps a casing, a shaft extend- WALTER FRED HARLOW. 

